View Full Version : Tank sealant??

01-25-2012, 01:02 PM
Well, another tank sealant thread. But what I would like to know is if any of you have used any of the available sealants on a NEW tank.

I'm looking for something that will work well with the tender tank I'm building for my live steam locomotive. It will hold water, not fuel. Because the tank will be riveted together like the prototype, the sealant needs to be more than just paint; it needs to seal along the seams and rivets.

I've heard from other live steamers that the tank sealants don't adhere well and that they will separate from the metal where it comes to an edge at any openings in the tank.

While I understand that an old rusty tank may give some tooth for the sealant to grip, this will be new metal. I could scuff sand the metal before assembly.

I called Caswell about theirs but I felt that the person I talked to blew me off. She answered my question by telling me to follow the directions on the can and put drywall screws in the tank and shake it. Well, I'm smart enough to know that the purpose of this is to knock off any loose rust, not to otherwise prep the metal for adhesion. When I tried to explain that this was new metal, she interrupted me and repeated the line about the screws and directions on the can. Her tone of voice made it clear that that was all the information I was going to get from her.

So to reiterate: If any of you have used tank sealers on new metal, did it adhere well, and what brand did you use? THANKS!

Video Man
01-25-2012, 02:21 PM
While looking into a coolant tank leakage on an EMD E9 locomotive, one of our rail museum members, a retired aircraft mechanic, recommended we look at aircraft fuel tank sealants. While I have no hands-on experience with this material, there is a lot of info on the internet about these products. One interesting discussion is here: http://www.vansairforce.net/articles/tank_sealant.pdf The material is copyrighted by the author, Paul Trotter.

Perhaps worth looking into....

01-25-2012, 03:16 PM
Thanks, Video Man. I'll bet that these products work as a failure at 15,000 feet could be troublesome. I'll check them out.

01-25-2012, 03:19 PM
I had a Mooney aircraft that had a leaking fuel tank and we sealed it with PPG's Pro-Seal sealent.
It was still holding 5 years later when I sold the airplane.

01-25-2012, 03:21 PM
Braze it! Much better then some 'sealant' :)

A good silver braze (Or even a decent silver solder but.. braze works so much better) would wickin to the joints like nobodys business. Brass braze can be coaxed into doing it too. But silver brazes can give you a water tight join the first time, with little experiance.

01-25-2012, 03:29 PM
Thanks, Seastar, I'll check that out.

Black Moons: Good idea but with a sheet metal tank I'd worry about distorting the sheets at that temperature. But you gave me the idea to experiment with soft solder, though. There's no pressure on the tank. But I also need to coat the interior against rust.

01-25-2012, 03:53 PM
Silver braze melts around 1100f, I never noticed any tank distortion on the stupidly thin formed tank I did it on to add another port, but then I can see reason for consern.

01-25-2012, 04:42 PM

I'm assuming the tank is now fully together and there is no way to actually access the tank? I will usually bead blast my tank prior to joining that way there is tooth. Hand sanding works too, but again, only if you have access. Acid etch is an option. It all depends on the type of tank. I'm assuming this is brass?

Aircraft tank sealant is all I've ever used and that's normally on a used fuel tank not new. Aircraft Spruce should have what you need. Not familiar with the Caswell stuff. Regardless, it must be a 2 part product or it's not worth purchasing...


01-25-2012, 05:01 PM
Boy, I have to say that using a soft solder would be easy, and if you pre-
fluxed it, it would be both quick and almost foolproof.

Downsides would be potential corrosion from the flux, and appearance.

Sandblasting the material before you assemble it would help a lot with mechanical
'keying' if you do decide to seal it internally...


01-25-2012, 05:20 PM
Thanks for the tips, guys.


The tank isn't built yet. I am trying to think of these things before it's too late. The material is 20 ga. steel sheet.

01-25-2012, 06:19 PM
At Northwest Airlines we used PRC 1422 for a general purpose sealant. I see it is now PR 1422. It was used for fuel cells and pressure sealant in the fuselage. Also used lots and lots to seal floor boards in the cabin and lavatory. Once it cures it is hard to remove. Ask the guys that had to chase leaks from a fuel cell. Like a leaking roof it comes out some where else.

01-25-2012, 06:34 PM
I don't remember the number but I have used a lot of PRC with good results. I don't know what it cost. The people that manufacture galvanized sheet metal water tanks coat the inside with a paintable sealant. I saw it being applied on tanks at the old Mueller facility at Balinger, TX. It works great and lasts for years.

01-25-2012, 07:25 PM
Second (or third) on the aircraft tank sealant. It is a very robust product, nearly impossible to remove once cured (assuming a reasonably clean surface) . It is available in high & low viscosity,"A" being the least viscous, "B" the most, and in different pot lives, from 15 minutes to 2 hrs.

This same product is used to seal the pressure vessel of pressurized aircraft.

01-25-2012, 08:55 PM
If you plan on using soft solder to seal the tank it will make the job easier if you tin all the surfaces that lap each other before you do any assemble.

01-25-2012, 09:05 PM
Glyptal red-


01-25-2012, 09:55 PM
Another tip if you soft solder- after tinning all the mating edges, brush on a thin coat of liquid resin flux before assembling the parts in alignment. Makes the flow-out of the solder so much easier.

01-25-2012, 10:24 PM
Well it looks as though there are several votes for the PRC 1422 by PPG Aerospace.

I think I'll super clean the metal before assembly with several wipes with solvent, wiping off the solvent before it dries to be sure all traces of oil and anything else is gone. I'll check with the mfg. to see what solvent to use. Then I'll hit the sheets while they are still flat (before bending to shape) with sandpaper to give some tooth for the sealant to grab. I also note there is a primer for this sealant, so after assembly, I'll use that. How does that sound?

The photo below IS NOT MY TANK, but a similar one so you can get an idea of what I'm up to. Mine will have smaller rivets, about 1600 of them!

Thanks everyone!


Mad Scientist
01-25-2012, 10:33 PM
The "Glyptal red" is a good suggestion.
Eastwood.com has both it and a gas tank sealer kit. The kit comes with a tank etching solution, a metal wash, and the sealer. I've used the sealer with good results. It is meant to stand up to fuels containing alcohol so it should be able to handle water.